The present invention relates to a method for data processing in which a determination is made as to whether or not thinning should be effected upon point data corresponding to a three-dimensional shape obtained along a surface having the three-dimensional shape.
Point data corresponding to a three-dimensional shape are obtained one after another at specified intervals along a surface having the three-dimensional shape (e.g., surfaces of machined parts or sample products) and contained and stored in a storage unit. The stored data can be used in testing the machined parts or preparing control data for use in the drawings of the sample products and NC (Numerical Control) processing thereof.
For instance, as seen in FIG. 5, point data D101 through D118 corresponding to a three-dimensional shape are obtained one after another along a surface having a three-dimensional shape, and are stored in a storage unit.
However, the number of point data to be stored in the storage unit is very large. Point data are extracted at short intervals to attain a correct correspondence to the shape of the surface having the original three-dimensional shape, so that the amount of data becomes very large. Thus, it is conceivable that the point data once stored in the storage unit are thinned so that particular point data only are restored and finally retained in storage. This arrangement leads to an increase in the total amount of information on the surface having the three-dimensional shape that can be stored and retained with the same storage capacity. Moreover, the arrangement also facilitates processing using the stored and retained point data.
Actually, if the point data are thinned at equal intervals so that only particular point data D101, D103, D106, D109, D112, D115, and D118 are stored and retained in the storage unit as seen in FIG. 6, the amount of point data that are finally left in the storage unit can be reduced.
However, even if the number of point data to be stored and retained can be reduced, only thinning the point data at equal intervals would give rise to another disadvantage in that a shape corresponding to the original shape could not be derived with high accuracy from the point data left in the storage unit. Although the original shape could be reproduced by a thick solid line S in FIG. 6 through graphical processing using a computer, the shape as shown by the thick solid line S in FIG. 6 does not correspond very well to the original shape as shown by a thin solid line T. In more detail, point data D111 and D116 at edge portions are omitted so that the edge portions cannot be reproduced correctly. Further, point data also are excessively omitted at rounded portions, so that the rounded portions cannot be reproduced correctly.